You probably don't need RouteCycle if: you ride the same route again and again, you train on the same hill, you already know your area very well and can build a good route fast, or you just need the shortest way from A to B. For these cases, any popular service like Garmin or Komoot is enough.
RouteCycle is for you if: you want to discover new attractions and new roads, and you are lazy to spend time planning where to go. Just open the app, set your distance, and ride.
Trips and bikepacking are another big one. Planning a multi-day route by hand can take many hours — picking quiet roads, sights, water points, places to sleep, and then stitching it all together day by day. My goal is to make RouteCycle build a great trip route in one click. We are not fully there yet, but this is the direction the project is heading.